In this work, major effort has been devoted in understanding the mechanism of spin exchange in oligonuclear systems. Emphasis has given on developing theoretical framework to quantify magnetic interaction in multielectronic polynuclear systems. The methods developed here can be used to derive exchange coupling constant in complicated systems much easily compared to existing protocols. In addition, the proposed formalism is capable of individual assessment of different exchange mechanisms, i.e. direct exchange and superexchange, which decides the magnetic ordering of any system. The study is extended to correlate spin coupling with other molecular properties such as aromaticity and non-linear optical (NLO) response.